Potentially fix #289

This needs some regression testing to ensure this is the right fix.

proxy/src/main/java/com/velocitypowered/proxy/connection/MinecraftConnection.java

@@ -30,6 +30,7 @@ import com.velocitypowered.proxy.protocol.netty.MinecraftEncoder;
 import com.velocitypowered.proxy.util.except.QuietDecoderException;
 import io.netty.buffer.ByteBuf;
 import io.netty.channel.Channel;
+import io.netty.channel.ChannelFuture;
 import io.netty.channel.ChannelFutureListener;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.ChannelInboundHandlerAdapter;
@@ -46,6 +47,7 @@ import javax.crypto.spec.SecretKeySpec;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.checkerframework.checker.nullness.qual.Nullable;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * A utility class to make working with the pipeline a little less painful and transparently handles
@@ -64,6 +66,7 @@ public class MinecraftConnection extends ChannelInboundHandlerAdapter {
   private final VelocityServer server;
   private ConnectionType connectionType = ConnectionTypes.UNDETERMINED;
   private boolean knownDisconnect = false;
+  private boolean disconnected = false;
 
   /**
    * Initializes a new {@link MinecraftConnection} instance.
@@ -236,12 +239,18 @@ public class MinecraftConnection extends ChannelInboundHandlerAdapter {
           this.setAutoReading(false);
           channel.eventLoop().schedule(() -> {
             knownDisconnect = true;
-            channel.writeAndFlush(msg).addListener(ChannelFutureListener.CLOSE);
+            channel.writeAndFlush(msg).addListener((ChannelFutureListener) future -> {
+              future.channel().close();
+              this.fireDisconnected();
+            });
           }, 250, TimeUnit.MILLISECONDS);
         });
       } else {
         knownDisconnect = true;
-        channel.writeAndFlush(msg).addListener(ChannelFutureListener.CLOSE);
+        channel.writeAndFlush(msg).addListener((ChannelFutureListener) future -> {
+          future.channel().close();
+          this.fireDisconnected();
+        });
       }
     }
   }
@@ -261,17 +270,28 @@ public class MinecraftConnection extends ChannelInboundHandlerAdapter {
           knownDisconnect = true;
         }
         channel.close();
+        this.fireDisconnected();
       } else {
         channel.eventLoop().execute(() -> {
           if (markKnown) {
             knownDisconnect = true;
           }
           channel.close();
+          this.fireDisconnected();
         });
       }
     }
   }
 
+  private void fireDisconnected() {
+    if (!disconnected) {
+      disconnected = true;
+    }
+    if (sessionHandler != null) {
+      sessionHandler.disconnected();
+    }
+  }
+
   public Channel getChannel() {
     return channel;
   }

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/LoginSessionHandler.java

@@ -117,8 +117,7 @@ public class LoginSessionHandler implements MinecraftSessionHandler {
       resultFuture.completeExceptionally(
           new QuietRuntimeException("The connection to the remote server was unexpectedly closed.\n"
               + "This is usually because the remote server does not have BungeeCord IP forwarding "
-              + "correctly enabled.\nSee "
-              + "https://docs.velocitypowered.com/en/latest/users/player-info-forwarding.html "
+              + "correctly enabled.\nSee https://velocitypowered.com/wiki/users/forwarding/ "
               + "for instructions on how to configure player info forwarding correctly.")
       );
     } else {